Fasting our patients in the critical care unit. How can we get it right?

Ella Segaran, Advanced dietitian for Critical Care, Imperial College Healthcare NHS Trust and Chair of the NAHP committee of the ICS, considers barriers to achieving nutritional targets in critical care and proposes some solutions.

On average critically ill patients only receive 50-60% of their nutritional target. As a critical care dietitian this causes me considerable frustration. I perform a detailed nutritional assessment, develop a feeding plan only to find the system is working against me. Underfeeding is associated with more infections and longer ICU and hospital stay. We know if we get it right and achieve more than 80% of the target we decrease mortality and ventilator days.

Why is it so hard to deliver nutrition targets? Evidence suggests interruption of enteral nutrition (EN) occurs on 60% of critical care days. . Culprits include fasting for theatre, extubation, tracheostomy, radiology and confirmation of nasogastric tube placement . Fasting often occurs for multiple extended periods over an ICU stay.

What is the argument for pre-procedure fasting? EN is stopped for a number of hours on the premise of avoiding aspiration of stomach contents. Whilst European and American recommendations advise on perioperative fasting for anesthesia, they are written for elective surgical patients eating food. They do not provide guidance for the fasting of intubated patients (with a theoretically protected airway) receiving EN via feeding tubes. Some argue that in these situations fasting is unnecessary as the feeding tube can be aspirated prior to procedure, thus leaving an empty stomach. Currently there is no evidence, and there are no internationally recognized guidelines, to shape our practices. We are left trying to balance the aspiration risk and the negative consequences of persistent underfeeding.

What are the direct consequences? At present, we observe varied clinical practices with in units and across the country; all resulting in extended fasting times. This is frustrating for nutrition-obsessed dietitians like me, the nurses and bad for the patients. We all hate inconsistent practices. It is also frustrating to hear a doctor saying “turn the feed off in preparation for ….”, and then not giving any guidance on how long the feed has to be off. If this is not kept in check, the patient can easily go 12- 24hrs without nutrition before someone notices.

It is also frustrating to hear a doctor saying “turn the feed off in preparation for ….”, and then not giving any guidance on how long the feed has to be off.

Which procedures cause the longest fasts? Extubation is probably the worst culprit as it is impossible to predict when it will occur. What normally happens (despite our guidelines stipulating a 4 hour fast), is that the junior doctors stop the feed at 4am in anticipation of extubation first thing. However, if the patient is not ready, they are given until the lunchtime ward round before the consultant gives the yay or nay. If they get the go ahead, they may be extubated by 4pm; 12hrs after the feed was originally turned off. This is the best-case scenario, as often the patient isn’t ready for extubation and at about 7pm, someone finally admits it’s not going to happen and suggests that perhaps the EN should be put back on again. The cycle repeats again the next morning. It’s not uncommon for this to go on for days. Once the patient is finally extubated, my pain and frustration is not over. Oh no. We now have to wait for days before re-starting EN just in case the patient gets re-intubated, or we wait for them to recover the ability to safely eat and drink. Is it surprising that we can only provide 50-60% of target?

Is the same fasting time necessary for all procedures? Two of the most common reasons for fasting are extubation and tracheostomy. These are often perceived as higher risk for aspiration than some other procedures, and therefore intensivists may be more reluctant to decrease fasting times, preferring to stick to the national recommendation of six hours. Procedures that do not involve manipulation of the airway in an already intubated patient, such as surgery and radiological procedures, may be viewed as lower risk and therefore clinicians might be more likely to allow a shorter fast.

There is a clear need to develop expert consensus statements on fasting for ICUs to guide clinical practice.

What can we do improve our current practice? There is a clear need to develop expert consensus statements on fasting for ICUs to guide clinical practice. This should focus on creating a pragmatic approach considering the risks and benefits of continuing EN right up until procedures commence. It is possible to make a difference. We have a ‘reduced hours fasting guideline’1 in our trust, which has been successfully used to increase EN delivery from 65% to 84% without any increase in complications.

So next time the patient you are looking after has their feed turned off for a procedure, please think about if it is necessary, and if it is how long should it be before it can be restarted.